In quite a number of types of equipment used in analyzing and operating oil wells, pressure accumulators are used so that operations may be carried out by utilizing differential pressures between the accumulator and pressures at other points within the equipment. In some equipment, the accumulator pressure is charged with pressured fluid at the surface and remains constant during all periods of use of the equipment. However it is desirable that accumulator pressures be adjustable after the tool has been run downhole and even at intervening times between different uses of the equipment. With the tool down in a well hole several or many thousands of feet below the earth's surface, it is not an easy thing to do to change the accumulator pressure at such a remote location. This invention seeks to provide apparatus and methods for adjusting pressure entrapped in an accumulator so that the accumulator may be used as a pressure reservoir and reference pressure for performing certain functions. In U.S. Pat. No. 4,415,027, an apparatus is disclosed for downhole recharging of accumulators, but the apparatus requires the use of a blanking off wire line tool and multiple valves. Other apparatuses are known in the art for performing accumulator recharging functions, but all suffer from serious defects limiting their utility.